Clathrina clathrus

"Clathrina clathrus" is a species of calcareous sponge belonging to the family Clathrinidae. This yellow sponge, up to 10 cm in diameter, usually appears cushion-shaped at a distance. Close-up the sponge can be seen to consist of a tangled mass of tubes. Like "C. coriacea", the spicules are exclusively three-pointed "triactines".